Microwave energy transmission and commutation coupler



May 14, 1968 H. SCHARFMAN- 3,383,596

MICROWAVE ENERGY TRANSMISSION AND COMMUTATION COUPLER Filed June 28, 1965 2 Sheets-Sheet 1 28 MICROWAVE 26 SIGNAL GENERATOR 2 l 1/ A /Z Q 1 '11 Iii \22 I: v T 4 4 I HQ 2 F/G. 1

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MICROWAVE ENERGY TRANSMISSION AND COMMUTATION COUPLER I Filed June 28, 1965 2 Sheets-Sheet 2 MICROWAVE SIGNAL N5? GENERATOR MICROWAVE SIGNAL \80 GENERATOR 76 82 84 a as 90 CAT 0 P T COMMUTATION oEglguplfiLNe H DE m u v GUN COUPLER AMPL'F'ER MEANS BEAMPAT" 561 5 copLEc'roR ELEMENTS i 78 IN VE'IV 72R HOWA RD SCHARFMA ATTORNEY United States Patent 3,383,596 MICROWAVE ENERGY TRANSMESSION AND 'COMMUTATION CGUPLER Howard Scharfman, Lexington, Mass, assignor to Raytheon Company, Lexington, B1355 a corporation of Delaware Filed June 28, 1965, Ser. No. 467,231 Claims. (Cl. 325--120) ABSTRACT OF THE DISCLOSURE An electron beam coupling device for transmission of microwave energy signals in a cicular pattern within an evacuated envelope over a predetermined path for subsequent radiation by discrete stationary antenna elements in a sequential manner without any mechanical components. Rapid scanning speeds may be realized, limited only by the speed of the electron motion.

The present invention relates broadly to the transmission of electromagnetic energy at microwave frequencies, and more particularly to an electron beam coupling device for the transmission and commutation of microwave energy signals to result in radiation thereof in any desired pattern configuration without any mechanical moving components.

Microwave radar systems commonly employ scanning antennas for the propagation and reception of signals at high power microwave frequencies over wide areas of space. It is conventional in such systems to feed microwave frequency signals through waveguide transmission lines to the antenna element which then must be rotated in the full azimuth plane of 360 for the detection of unknown distant objects. The antenna elements are rotated at rapid rates of speed to assure complete coverage of the area scanned. Complicated and cumbersome electromechanical rotary joints have been devised in the art to fulfill the necessity of coupling the microwave signals to the antenna feed horns together with the full rotational capacity. With higher speeds of rotation being continually required to be compatible with higher frequencies of the energy the extent of the capability or construction of mechanical rotary joints has been expended to the fullest limits. Additional problems have also plagued the use of mechanical rotary joints in that the electrical parameters must be carefully designed and controlled to assure etficient transmission and reception with the antenna elements employed.

It is an object of the present invention to provide a new and novel transmission and commutator coupler for the direction of microwave energy signals in a predetermined scanning pattern.

Another object of the present invention is the provision of an electronic transmission and commutator coupler of microwave signal energy having no mechanical components.

Still another object of the present invention is the provision of apparatus for the propagation of microwave energy signals utilizing an electron beam as the vehicle for the coupling and commutation of such signals from external operation means to the antenna radiating elements to achieve a predetermined scanning pattern.

The invention briefly comprises the coupling of external microwave frequency signals to an electron beam within an evacuated envelope and the transmission of the modulated beam to a microwave circuit network including filed antenna elements for radiation of the microwave energy signals in a predetermined pattern. In one embodiment of the invention the microwave modulated beam may be commutated to couple the high powered ice electromagnetic energy sequentially to a plurality of discrete circularly disposed decoupling elements. Radiation of the circular pattern will thus be permitted. In view of the rotational speeds of tens of megacycles per second or greater utilizing an electron beam, high power microwave signals may be transmitted at rapid speeds heretofore unattainable with conventional mechanical structures. In other embodiments of the invention selective transmission patterns may be realized by means of de flection elements to switch the beam between discrete positions along an array of microwave circuit decoupling elements. Amplification of the microwave energy signals may also be practiced by the incorporation of suitable structure between the beam coupling means and the commutation means for propagation of the amplified and modulated beam to evolve the desired antenna radiation patterns.

Other objects, features and advantages will become apparent after consideration of the following detailed description together with the accompanying drawings in which:

FIG. 1 is a longitudinal cross-section view of an illustrative embodiment of the invention;

FIG. 2 is a view along the line 2-2 in FIG. 1 and a pictorial representation of the radiated antenna pattern;

FIG. 3 is a longitudinal cross-sectional view of an alternative embodiment of the decoupling network utilized in the invention;

FIG. 4 is a view along the line 44 in FIG. 3 illustrative of the deflection means of the invention;

FIG. 5 is a view along the line 55 in FIG. 3 illustrative of the decoupling network array of this embodiment;

FIG. 6 is a partial longitudinal cross-sectional view of he input end of the over-all embodiment illustrative of an alternative microwave signal input coupling means; and

FIG. 7 is a block diagram illustrative of an embodiment incorporating amplification means in the over-all device.

Referring to FIGS. 1 and 2, the embodiment of the invention shown comprises an evacuated envelope 2 of a dielectric material having an electron emitter 4 disposed at one end. Any conventional cathode gun type structure with an emitting surface and an indirectly heated filament together with accelerating and focusing means for the generation of an electron beam may be employed. Adjacent to the beam generation means is a microwave coupling element 6 to provide for the coupling of electromagnetic energy signals at microwave frequencies generated by the source 8 to the electron beam indicated by the dotted lines 10. The impressing of the microwave signals on the beam will result in this beam becoming AC modulated at the microwave frequency level. Hence, pulse or continuous wave microwave energy at power levels commensurate with the apparatus employed may be carried by the beam.

The coupling means shown illustratively as a helix 6 may also consist of a grid or distributed delay line as well as other coupling devices employing resonant cavities. The over-all invention therefore is not specifically limited to the selected type of microwave energy coupling means illustrated in the drawing.

The microwave modulated electron beam next traverses a plurality of commutating means shown illustratively as quadrature deflection plates of the type employed in cathode ray tubes with two opposing plates 12 and 14 being shown. By means of suitable differential voltage biasing potentials applied to the deflection plates the electron beam may be swept in a circular fashion or angularly deflected. Through the section of the envelope indicated generally by the numeral 16 the dotted lines have been shown to indicate rotation of the subject moduiated beam. An external magnet such as a solenoid 18 or other suitable focusing means surrounds this portion of the envelope to provide a magnetic field in the direction parallel to the axis of the tube envelope. The magnetic field provides for the confinement of the electron beam along the desired path and establishes a focusing action.

At the other end of the tube envelope a decoupling network consisting of a plurality of microwave energy responsive elements is disposed. A series of fixed spaced discrete elements 26 have been shown disposed in a circular array to define a cylinder through which the rotated beam passes. The spacing between the elements is carefully selected to provide in effect resonant slots through which microwave energy signals may be radiated. Such elements are indicated by the numeral 20 and the radiating slots 22. As the electron beam 10 is rotated in the direction indicated by the arrows 24 in FIG. 2, the microwave signal energy wil be in close proximity to the responsive circuit elements to result in decoupling of this energy from the beam. A biconical antenna radiator com} prising sections 26 and 28 surrounds the decoupling network to thereby direct the microwave signal energy into free space in a pattern shown pictorially in FIG. 2 and indicated by the numeral 36. Since the electron beam is rotated at very high speeds it sequentially traverses the microwave decoupling circuit and by the combined effects of this beam and the decoupling network a scanning pattern in a full 360 area evolves without employment of any movable mechanical components. The antenna radiators 26 and 28 have inclined surfaces provided to assure the directivity of the radiated energy in accordance with conventional antenna systems procedures. The output signals will be generated at extremely high speeds in view of the fact that the electron beam is propagated at speeds in megacycles per second to thereby provide a distinct advantage over rotational speeds attainable with mechanical structures.

With the microwave frequency energy signals decoupled from the electron beam this beam passes to the collector electrode 32 and suitable cooling structure may be provided to allow for any residual microwave energy not decoupled in the antenna network structure. The electron emitter means 4 as well as collector electrode 32 are suitably biased by external potential voltage biasing means 34 coupled thereto by means of leads 36 with the biasing values determined in accordance with well known teachings in the art which need not be further enumerated in this specification.

In FIGS. 3 and 4 the left hand portion of the over-all embodiment is similar to and accordingly numbered to the view in FIG. 1. In FIG. 4 the quadrature deflection plate means 12, 14 and 38, 40 are shown connected to a variable deflection potential supply 42 for biasing opposing pairs of the plates for the provision of a circular sweep movement or switching the radiated antenna pattern between discrete elements by angularly deflecting the electron beam 10 in the desired manner.

An alternative decoupling network is further illustrated in FIG. 3 at the right hand portion of the over-all embodiment and in FIG. 5. The microwave frequency responsive elements 44 are again disposed in a circular array to provide for the traversal of the modulated electron beam sequentially past each of the RF circuit structures. Each of said structures incorporates a plurality of interdigital delay line finger members 46 with the dimensiOnS thereof selected to afford appropriate microwave signal responses at specific frequencies. The output connection for the microwave energy generated on the interdigital delay line structure 44 comprises a forwardly disposed output connector 48 with the center conductor communicating antenna elements 50 in each of said delay line structures. In this way a radial array of antenna radiator elements as shown in FIG. 5 is evolved in what may be referred to as an end-fire antenna array. Each of the antenna radiator or dipole elements may be activated sequentially by means of the rotary beam or selectively as desired.

Turning next to FIG. 6 another possible configuration of the invention is shown. Microwave energy from the external generator 52 is coupled by means of coaxial conductor 54 to a resonant cavity 56 having a plurality of parallel oppositely disposed plates 58 and 59. To couple the microwave frequency energy signals from the external source an electron beam 61'? from cathode gun emitter s2 passes through the resonant cavity by means of irises 64 and 66. Magnetic field producing means 72 extend parallel to the resonant cavity to provide an axial magnetic field. As the electrons enter the resonant cavity interaction with the combined transverse electric field indicated by the arrow 74 and the axial magnetic field will cause the electrons to spiral with increasing radius as they proceed through the cavity. The rotating beam will acquire the microwave power modulation from the external source and transfer this modulated beam throughout the length of the tube envelope to the decoupling networks shown in the previous views FIGS. 1 and 3.

The microwave energy absorbed by the beam and the input cavity 56- thus not only establishes the necessary alternating fields for the rotation of the beam at extremely high speeds but amplitude modulates the beam to result in an efiicient power transfer device. Since the electron beam receives the rotational energy from the transverse electric field and magnetic field in the resonant cavity, it is this rotational energy which is removed by the decoupling network. If all the rotational energy is extracted from the beam the electron beam will arrive at the collector electrode with only axial velocity and no rotational velocity. Any residual rotational energy which is not extracted will still go to the collector electrode. The resonant cavity is tuned to the cyclotron frequency of the magnetic field which is parallel to the axis of the tube.

In FIG. 7 additional combinations utilizing the structure of the present invention will be evident. A block diagram has been shown with the appropriate components labeled since such components have been specifically described hereinbefore. The cathode gun 76 is disposed adjacent to the input coupler 73 to which is connected the microwave signal generator 83*. In this embodiment the modulated electron beam may be further amplified by means of amplifier 82 disposed between the input coupler and the commutation means comprising deflection plates 84. After traversing the beam path 86 the beam then proceeds to the decoupling network 88 where the microwave modulated signals are removed and the electron beam is collected by the electrode 96. In this embodiment the amplifier section may be of the conventional traveling wave, coupled cavity or klystron type to provide the desired amplification.

There is thus disclosed in a single integral structure a novel transmission and commutator coupling device to provide for the radiation of microwave energy signals in a predetermined scanning arrangement. Rotation or deflection of the electron :beam for the activation of fixed spaced discrete decoupling network members facilitates the radiation of the signals without reliance on any mechanical movement to accomplish this purpose. In view of the exceedingly high speeds attainable through the commutation of an electron beam, the transfer of microwave energy signals is achieved at much higher speeds than heretofore attainable with rotary antenna coupling joints of the mechanical type. High peak as well as average microwave powers may be readily transferred in accordance with present day technology in the provision of cornponents for handling such powers. While specific antenna radiator structures have been illustrated, it will be realized that any array of elements may be employed. In addition, the device disclosed herein not only serves as a power transfer device for antenna arrays but may be readily adaptable to switching functions between waveguide transmission lines simply by control of the propagation characteristics of the modulated electron beam in relation to the fixed output decoupling elements. Other modifications will also be apparent to those skilled in the art which do 'not depart from the scope of the broadest aspects of the present invention as defined in the appended claims.

What is claimed is:

1. A microwave energy transmission and radiation device comprising:

an evacuated envelope;

means for generation of an electron beam disposed at one end of said envelope;

means for coupling externally generated microwave frequency signal modulations to said beam;

means for directing said modulated beam in a circular path;

a circular array of discrete microwave frequency responsive circuit means disposed within said envelope to decouple the microwave energy signals when said modulated beam is transmitted in close proximity thereto; and

radiation means associated with said decoupling means to direct said signals into space in accordance with the pattern determined by the combined effects of the beam directing and decoupling means.

2. The combination according to claim 1 wherein said decoupling means comprise stationary spaced elements defining sections of interdigital delay line slow wave structures.

3. The combination according to claim 1 wherein said radiation means comprise stationary oppositely disposed biconical radiator antennas positioned in close proximity to said decoupling means.

4. The combination according to claim 1 wherein said microwave energy signal modulation coupling means comprise a resonant cavity having centrally disposed opposing parallel plate members defining a path through which said electron beam is propagated and transverse electric and magnetic fields associated with said cavity to impart rotational energy to said beam.

5. The combination according to claim 1 wherein amplification means are disposed between said coupling means and beam directing means.

6. In combination:

an evacuated envelope;

means for generation of an electron beam disposed at one end of said enevelope;

means for coupling externally generated microwave frequency energy signal modulation to said beam;

means for deflecting said beam along the longitudinal axis of said envelope in a predetermined path;

a circular array of discrete microwave frequency responsive circuit means disposed adjacent to the opposite end of said envelope to selectively decouple said microwave signal; and

radiation means associated with said circuit decoupling means to direct said microwave signals into space in accordance with the selected pattern determined by the combined efiects of said deflected beam 'annd decoupling means.

7. A microwave energy transmission and commutator coupling device comprising:

an evacuated envelope;

a cathode gun emitter assembly for producing an electron beam disposed at one end of said envelope;

a helical conductor having a central passageway through which said electron beam is launched and an external microwave frequency energy signal source coupled to said helical conductor to modulate said beam;

a plurality of deflection plate members disposed along said beam path and biased by an external source of voltage potential to direct said electron beam in a predetermined path;

a circular array of fixed spaced discrete microwave energizable output members disposed adjacent to the opposite end of said envelope to decouple said microwave signals as said beam illuminates each of said members; and

stationary antenna radiator members associated with said decoupling members to cause said microwave signals to be radiated in space in accordance with the scanning pattern determined by said electron beam path and positioning of said decoupling members.

8. A microwave energy transmission and commutator coupling device according to claim 7 wherein a microwave energy amplifier is disposed between said helical conductor and deflection plate members.

9. A microwave energy transmission and commutator coupling device comprising:

an evacuated envelope;

a cathode gun emitter assembly for producing an electron beam disposed at one end of said envelope;

a resonant cavity having centrally disposed opposing parallel plate members defining an electron beam path therebetween and transverse electric and magnetic fields associated with said cavity to impart rotational energy to said beam;

input microwave frequency energy signal conductor means coupled to said cavity to modulate said beam;

a circular array of fixed spaced discrete microwave energizable output members disposed intermediate to the ends of said envelope to decouple said microwave signals as said beam illuminates each of said members; and

stationary antenna radiator members associated with said decoupling members to cause said microwave signals to be radiated into space in accordance with a predetermined scanning pattern.

10. A microwave energy transmission and commutator coupling device according to claim 9 wherein a microwave energy amplifier is disposed along said beam path after said resonant cavity.

References Cited UNITED STATES PATENTS 1,941,303 12/1933 Heintz 325-121 2,235,527 3/1941 McArthur 31S39.3 2,380,981 8/1945 McElhannon 343-701 2,547,631 4/1951 Evans 332-58 X 2,925,521 2/1960 Dench 3 l5--3.6 2,955,226 10/1960 Currie et a1. 3153.6 3,116,485 12/ 1963 Carson 343773 X ROBERT L. GRIFFIN, Primary Examiner.

JOHN W. CALDWELL, Examiner.

B. V. SAFOUREK, Assistant Examiner. 

